Hydraulic system



Nov. 12, 1946. W.ERN ST 2 ,410,869

HYDRAULI C SYSTEM Filed Nov. 12, 1942 INVENTOR WALTER ERNST BY ATTQRNEY Patented Nov. 12, 1946 UNITED STATES ATENT OFFICE 2,410,869 HYDRAULIC SYSTEM Walter. Ernst, Mount Gilead; Qhio, assignor to The Hydraulic Development Corp., Inc.,-Wilmington, Del., a corporation of Delaware Application November 12., 1942, Serial No. 465,521

1 This invention relates to hydraulic systems and, in particular, to hydraulic systems comprising a fluid operable plungerand means for controlling the speed of said plunger.

It is an object of this invention to provide a hydraulic system including a fluid operable plunger, in which valve means is provided for controlling the speed-of said plunger. said valve means being controlled in response to the travel of said plunger so as to vary the speed thereof. 14)

-vide an open hydraulic circuit including a plunger and fluid operable advancing and retracting means for reciprocating said plunger, in

Which the retracting means is hydraulically -30 does not form a part of the present invention nected with a plurality of throttle valves, one'of which may be made inefl'ective in response to a predetermined travel of said plunger.

These and other objects and advantages of the invention will appear more clearly from the' a nduit 21 with a conduit 22 leading to thefollowing specification in connection with the accompanying drawing illustrating, by way of example, a hydraulic system according to'the. invention.

4 Claims. (or. 60-52) 2 Connected to the valve cylinder II is. a conduit l2 which leads to a conduit l3.- The-conduit l3 includes an adjustable choke l4 and has one end connected to a four-way valve, generally designited l5, while the other end'of the conduit 43 leads to a conduit It. The conduit l6 comprises an adjustable choke valve l'land is con- .nected, on one hand, with the interior of the valve cylinder Land on the other hand with a fluid reservoir or surge. tank 18;. The tank I8 is mounted on flanges IS on the cylinder i, which latter is provided with a surge ,valve 20.

The surge valve 20 is adapted, in response to a predetermined pressure in the lower portion of the cylinder 1, to open, to thereby establish fluid -connection between the upper portion of the cyl- I inder l and the tank l8. The surge valve also 1 opens in response to a suction eflect in the upper poftion of the cylinder I. The surge valve 20 and for a more detailed description thereof reference may be had to U. S. Patent No. 2,193,248

' to Ernst.

The surge valve 20 is connected, by means of lower portion of the cylinder l. The conduit 22 also leads to the interior of the valve IS, in which are reciprocably mounted the piston portions 23 and 24 of a valve member 25. The valve memn ral. the st m ac ordin to the n \ber 25 is provided with a handle 26 to allow manent invention comprises \a reciprocable plunger having associated therewith fluid operable advancin and retracting means for actuating said plunger, and a plurality of throttle valves u'al operation thereof. The lower end of the valve member 25 has adjustably mounted thereon a coliar2'l adapted to engage one end of a lever 28 which is shiftable about'a pivot 291. and

through which the fluid expelled m the 5 comprises alever arm 30 adapted to be'engaged tracting means, escapes during a part of the working stroke of said plunger.

When the plunger, during its working'stroke, has reached a predetermined position, valve by the press platen 4.

The arrangement is such that when the platen 4 approaches its retracted position, it engages the arm 30 and shifts the latter in anti-clockmeans is actuated which makes one of said wise direction in sucha manner that the lever throttle valves inefiective, thereby forcing the fluid expelled from the retracting means through the remaining valve, with the result that the speed of the plunger is slowed down.

Referring now to the drawing in detail,-the

system shown therein comprises a cylinder I having reciprocably mounted therein a press ram 2 including a double-actin piston 3. Connected to the ram 2 is a platen 4 carrying a cam 5. The

arm 28 engages the collar 21 and thereby causes the valve member 25 to move into the position shown in the drawing, in which position the conduits 2| and 22 and the conduit 3|, leading to the upper portion of the cylinder l, are closed off, while fluid connection between any of the conduits 32-, 33 and-34 is interrupted. The conduit 34 communicates with the pressure side of cam 5 is adapted, at a predetermined point of a fluid $911113!v 35, which may, for instance be travel of the ram 2, to engage a roller 6 and to shift the valve member I, connected to said roller 6, toward the left against a spring 8. The valve member I has two piston portions 9 and In revariable delivery pump of the radial piston type or of the vane type, and may be provided with servo-motor means 36 connected through a pilot line 31 with the conduit 34 for moving the pump ciprocably mounted in the valve cylinder ll. to substantiallyn- 'elivery position when a pre- 3 determined pressure is established in the conduit 34.

The system according to the present invention operates as follows:

It may be assumed that all parts occupy the position shown in the drawing, and that it is now desired to perform a working stroke of the ram 2. To this end, the valve member 25 is shifted into its lowermost position, in which fluid connection is established between the conduits 3I and 34, while the conduits 22 and 33 are in hydraulic communication with each other.

If the pump 35 is in operation, it now delivers pressure fiuid through the conduits 34 and 3I into the upper portion of the cylinder I. Inasmuch as now fluid connection is established bethe lower portion of the cylinder 1 passes through conduits 22 and 33, in part through the choke I4 and in part through the conduit I2, valve cylinder I0 and choke I1 into the tank I8. The fluid delivered by the pump 35 into the upper portion of the cylinder I is supplemented by fluid passing from the tank I8 into the upper portion of the cylinder I through surge valve s p When the platen 4 approaches a predetermined position, the cam 5 engages the roller 6 and shifts the valve member I toward the left so as to interrupt fluid connection between the conduit I2 and I6 through the valve cylinder II. Consequently, all the fluid expelled from the lower portion of the cylinder I must now pass through I4, thereby causing a reduction in the speed of the ram 2.

While the ram 2 continues its downward movement, the cam 5 will, in response to a predetermined travel of the ram 2, again disengage the roller 6, so that the spring 8 ,will return the valve member I to the position shown in the drawing. This will re-establish fluid connection between the conduits I2 and I6 through the valve cylinder I I, so that a part of the fluid expelled from the lower portion of the cylinderI may again pass through the throttle valve II. As a result thereof, the ram 2 increases its speed.

When the ram 2 has reached the end of its working stroke, the valve member is shifted into its uppermost position, in which fluid connection is established between the conduits 3:I and 22, while the conduit 3| is in fluid communication with the conduit 32.. Consequently, pressure fluid delivered by the pump passes through the conduits 34 and 22 to the lower portion of the cylinder I and moves the ram 2 upwardly, while fluid expelled from the upper portion of the cylinder I escapes through the conduits 3I and 32, and through the conduit I6 into the tank I8. Inasmuch as, at this stage, no fluid has to pass through the throttle valves I4 and I I, the retraction stroke of the ram 2 is efiected at relatively high speed.

When the ram 2 has reached the end of its retraction stroke, it again occupies the position shown in the drawing, in which the lever arm 30 has been shifted by the platen 4 into the position shown in the drawing, in which the lever arm 28 has moved the valve member 25 into its interportion of the cylinder I, nor be introduced to the upper portion of the cylinder I, so that the ram 2 comes to a halt. The system is now ready for a new cycle.

In connection with the retraction stroke of the ram 2, it may be emphasized that the valve member I, when temporarily actuated by the cam 5..

does not cause any change of operation, since the supply of fluid to and withdrawal of fluid from the cylinder I during the retraction stroke of the ram 2 is in no way aifected by the throttle valves I4 and I1 and the valve member I.

It will be understood that I desire to comprehend within my invention-such modifications as come within the scope of the claims.

Having thus fully described my invention, what I claim as new and desire to secure by Letters Patent is:

' 1. In a hydraulic system, reciprocable plunger means, fluid operable advancing and retracting means associated with said plunger means, a pump for supplying actuating fluid to said advancing and retracting means for reciprocating said plunger means, inlet conduit means hydraulically connecting said pump with said advancing means, exhaust conduit means hydraulically connecting said retracting means with exhaust, a valve member in said inlet and exhaust conduit means controlling the supply of fluid to, and the exhaust 0f fluid-from, said advancing and retracting means, a first adjustable choke means in said exhaust conduit, a second adjustable choke means arranged in parallel with said first choke means by conduit means establishing fluid connection between the inlets of said choke means, valve means in said last mentioned conduit means and automatically operated in response to a predetermined advancing movement of said plunger to interrupt'said fluid connection and also automatically operated in response to a predetermined additional advancing movementof said plunger for re-establishing said fluid connection, and said valve member being operated in response to a predetermined retracting movement of said plunger to cut off said inlet and exhaust conduit means.

2. In a hydraulic system, a downward acting plunger'having advancing and retracting means, a fluid source, a valve member movable into a first position to connect said source with said advancing means while simultaneously connecting said retracting means with a first exhaust conduit or, into a second position to connect said source with said retracting means while connecting said advancing means with a second exhaust conduit or, into a third position to interrupt fluid communication of said source with said advancing and said retracting means, paralleled choke valves in said first exhaust conduit for restricting the exhaust of fluid from said retracting means, normally open valve means between said valve member and one of said choke valves, means automatically responsive to the movement of said plunger during its advancing movement for first closing and thereafter opening said valve means for temporarily slowing down the rate of advancing movement of said plunger, and means operated by said plunger at the end of its retracting movement for moving said valve member into said third position.

3. In a hydraulic system, a downward acting plunger having advancing and retracting means, a fluid source, a' valve member movable into a first position to connect said source with said advancing means while simultaneously connecting said retracting means with a first exhaust conduit or, into a. second position to connect said source with said retracting means while connecting said advancing means with a second exhaust conduit or, into a third position to interrupt fluid communication of said source with said advancins and said retracting means, paralleled choke valves in said first exhaust conduit for restricting the exhaust of fluid from said retracting means, means automatically operated by said plunger during the advancing movement thereof for first interrupting flow of fluid from said retracting means through one of said choke valves and thereafter again establishing said. flow for temporarily slowing down the advancing speed of said plunger, and means adapted for operation by said plunger at the end of the retracting movement thereof for moving said valve member into its third position.

4. In a hydraulic system, a, reciprocaiole plunger having advancing and retracting means, a

fluid source for supplying said means, a valve member in the connection from said source to said means movable into a first position to connect said source with said advancing means while simultaneously connecting said retracting means with an exhaust conduit or, into a second position to connect said source with said retracting means while freely exhausting said advancing means or, into a third position to interrupt fluid communication of said source with said means, paralleled flow restricting means in said conduit for restricting the exhaust of fluid from said retracting means, means automatically operated by said plunger during its advancing movement for interrupting the flow of fluid through one of said flow restricting means, means automatically operated by a further advancing movement of .said plunger for again establishing fluid flow through said one flow restricting means, and

means automatically operated by said plunger during the retracting movement thereof for moving said valve member into its third position. WALTER ERNST. 

